Electrochemical cells are energy conversion devices and usually are used to collectively indicate fuel cells and electrolyzer cells. Fuel cells have been proposed as a clean, efficient and environmentally friendly power source that has various applications. A conventional proton exchange membrane (PEM) fuel cell includes an anode, a cathode, and a selective electrolytic membrane disposed between the two electrodes. A fuel cell generates electricity by bringing a fuel gas (typically hydrogen) and an oxidant gas (typically oxygen) respectively to the anode and the cathode. In reaction, a fuel such as hydrogen is oxidized at the anode to form cations (protons) and electrons by the reaction H2=2H++2e−. The proton exchange membrane facilitates the migration of protons from the anode to the cathode while preventing the electrons from passing through the membrane. As a result, the electrons are forced to flow through an external circuit thus providing an electrical current. At the cathode, oxygen reacts with electrons returned from the electrical circuit to form anions. The anions formed at the cathode react with the protons that have crossed the membrane to form liquid water as the reaction by-product following ½O2+2H−+2e−=H2O.
On the other hand, an electrolyzer uses electricity to electrolyze water to generate oxygen from its anode and hydrogen from its cathode. Similar to a fuel cell, a typical solid polymer water electrolyzer (SPWE) or proton exchange membrane (PEM) electrolyzer includes an anode, a cathode and a proton exchange membrane disposed between the two electrodes. Water is introduced to, for example, the anode of the electrolyzer which is connected to the positive pole of a suitable direct current voltage. Oxygen is produced at the anode by the reaction H2O=½O2+2H−+2e−. The protons then migrate from the anode to the cathode through the membrane. On the cathode which is connected to the negative pole of the direct current voltage, the protons conducted through the membrane are reduced to hydrogen according to the equation 2H++2e−=H2.
A typical electrochemical cell employing PEM comprises an anode flow field plate, a cathode flow field plate, and a membrane electrode assembly (MEA) disposed between the anode and cathode flow field plates. Each reactant flow field plate has an inlet region, an outlet region, and open-faced channels to fluidly connect the inlet to the outlet, and provide a way for distributing the reactant gases to the outer surfaces of the MEA. The MEA comprises a PEM disposed between an anode catalyst layer and a cathode catalyst layer A first gas diffusion layer (GDL) is disposed between the anode catalyst layer and the anode flow field plate, and a second GDL is disposed between the cathode catalyst layer and the cathode flow field plate. The GDLs facilitate the diffusion of the reactant gas, either the fuel or oxidant, to the catalyst surfaces of the MEA. Furthermore, the GDLs enhance the electrical conductivity between each of the anode and cathode flow field plates and the electrodes.
One of the questions that have to be answered in the design of such electrochemical cells is how to ensure the MEA works properly while preventing leakage of process fluids. This almost always involves proper support of the MEA when the electrochemical cell stack is assembled Extensive efforts have been made in this regard. However, these efforts have been focused on design changes of reactant flow field plates, which are complicated and expensive Compromise has to be made in these designs and hence this often results in the substitution of one problem for another.